1. Field of the Invention
This invention relates generally to an economizer for regulating the flow of outdoor ambient air into an enclosure to be conditioned. More specifically, the present invention concerns a damper and drive arrangement for controlling outdoor ambient air flow into an air conditioning unit.
2. Prior Art
A typical rooftop type packaged air conditioning unit includes a refrigeration circuit having a compressor, a condenser, an evaporator and an expansion device. The unit is divided into an indoor section wherein indoor air is circulated from the enclosure to the unit and is circulated by a fan back to the enclosure after being appropriately conditioned. An economizer for allowing outdoor ambient air to enter the indoor section may also be provided. The outdoor section typically includes a compressor and condenser as well as an outdoor fan for circulating outdoor ambient air in heat exchange relation with the condenser.
To effectively utilize the economizer, outdoor ambient air is circulated to the indoor section of the unit and to the enclosure when the temperature of the ambient air is such that cooling is provided without operation of the refrigeration circuit. Typical control systems for regulating flow of outdoor ambient air into the indoor section of the air conditioning unit include rotatable damper blades for effecting volume flow rate control of the outdoor ambient air entering the unit. These economizer dampers are often controlled by an electric motor and often have just open and closed positions or a small number of selected positions. Sophisticated electric motors are available for regulating dampers in numerous positions, however, such devices are costly and may require sophisticated control circuitry. Additionally, rotatable damper blades are difficult to seal and typically there is air leakage therethrough when the blades are in a closed position.
The herein described economizer apparatus concerns utilizing a solid sliding door in combination with a frame defining an opening such that a single solid member is positioned to regulate the size of the opening through which outdoor ambient air may enter the unit. A motor is connected to a shaft which is connected to the door via a drive rod. The motor is designed to turn the shaft at very slow speeds such that an approximately one-half shaft revolution results in complete opening and closing of the door thereby moving the economizer between the fully open and fully closed positions. The drive rod is capable of being rotated by the shaft and sliding such that the distance between the shaft and the pivot point to which the rod is connected to the door varies as the door is slid between positions. The solid door allows for a minimum leakage sealed closing of the opening for allowing the ambient air to enter the unit and provides for positioning the door at any position to regulate the flow of air into the unit. Additionally, a relatively inexpensive motor, such as a motor used for directly rotating television antennas may be utilized to position the door in any location. Other motors would also be acceptable.